By Cheryl Pellerin
USINFO Staff Writer

Washington – NASA’s next mission to the surface of Mars is scheduled to launch in August on a 10-month voyage to find out if water frozen in the planet’s northern polar region ever has been able to sustain microbial life.

The Phoenix mission consists of a spacecraft partially built for NASA’s cancelled 2001 Mars Surveyor Program, and a robotic lander that carries an advanced set of research tools never before used on Mars.

“It will be a robotic mission but we can all participate from Earth,” said Peter Smith, Phoenix principal investigator at the University of Arizona-Tucson, during a July 9 press briefing in Washington, “as we find for the first time what the environment is like on Mars, where ice is near soil on the surface. This will be a first.”

Smith leads the Phoenix mission, with project management based at the NASA Jet Propulsion Laboratory (JPL) in California and the development partnership based at Lockheed Martin in Colorado.

International contributions to the mission have come from the Canadian Space Agency, the University of Neuchatel in Switzerland, the University of Copenhagen in Denmark, the Max Planck Institute in Germany and the Finnish Meteorological Institute.

NASA's long-term Mars exploration program has four science goals – to determine whether Mars ever supported life, to characterize the planet’s climate and geology, and to prepare for human exploration.

To support these goals, Phoenix will study the history of water in the Martian arctic, search for evidence of a habitable zone and assess the biological potential of the ice-soil boundary.

Like all the other Mars exploration vehicles, Phoenix will “follow the water,” said Doug McCuistion, Mars exploration program director at NASA headquarters in Washington.

SCOUTING MARS

NASA’s Mars program consists of orbiters that perform remote reconnaissance of the planet from space, and landers that explore the surface directly, McCuistion said.

Phoenix is the first of a program of competitively proposed, relatively low-cost missions to Mars called the Mars Scout Program. Phoenix, chosen in 2003, saves money by using a lander structure, subsystem components and a protective heat shield built for a 2001 mission that was canceled while in development. The mission, including launch, will cost and estimated $386 million.

Once the spacecraft reaches the planet in May 2008, it will hit the atmosphere at 20,277 kilometers per hour, said Barry Goldstein, Phoenix project manager at JPL, and the heat shield at the bottom of the entry vehicle will absorb most of the energy of “a very rough ride.”

The spacecraft will land using thrusters to slow its descent just before touchdown, rather than airbags like those that the Mars exploration rovers Spirit and Opportunity used in 2004. (See related article.)

When the spacecraft is descending at a speed of 1,207 kilometers per hour, a supersonic parachute will deploy and the craft will continue to descend through the thin Martian atmosphere. As the lander approaches the surface, the shield will drop off, lander legs will deploy and pulsed thrusters will fire. Just before the craft touches down, it will turn itself so that it lands in a position that will ensure the best exposure to sunlight for its solar arrays.

After the dust settles – about 30 minutes – the lander’s equipment will begin to deploy. First, the solar arrays, then the camera and a meteorological mast. A day or two later, the 2.3-meter-long robotic arm will deploy. It is jointed at the “elbow” and “wrist,” and has a camera and a scoop.

DIGGING FOR CLUES

The robotic arm is designed to dig about 50 centimeters into a layer of ice that is expected to be within a few centimeters of the soil-covered surface. The camera and scoop will examine soil and ice.

"Phoenix has been designed to examine the history of the ice by measuring how liquid water has modified the chemistry and mineralogy of the soil," Smith said.

The arm will lift samples to two instruments on the lander's deck. One, the thermal evolved gas analyzer, will use heat to check for volatile substances such as water and carbon-based chemicals that are essential building blocks of Earth-type life forms.

The instrument is basically an oven that cooks surface soils and ices until they release gases trapped inside, Smith said, “but also we can detect organic materials. We can’t tell whether it’s DNA or proteins, but we can tell they’re complex organics.”

The term “organics” refers to materials that contain carbon compounds. Organic material can be derived from living and nonliving sources.

The other instrument – the Microscopy, Electrochemistry and Conductivity Analyzer – analyzes soil chemistry, and can tell the scientists if ice has melted in the recent past.

The mission will take about three months. Following its completion, the lander will function as a weather station until northern winter arrives and the sun sets, leaving the lander without power.

The lander will be exploring an area distant from that explored by the Mars rovers, Smith added. “We’re landing at about 70 degrees north. That same latitude and longitude on Earth is the middle of the Siberian permafrost.”

More information about the Phoenix mission and the Mars program is available at the NASA Web site.